Drippage prevention system and method of operating same

ABSTRACT

A drippage prevention system including: a first automatic control valve (ACV), an input of the first ACV fluidically connected to a source of fluid to be dispensed, the first ACV having a position ranging from fully closed to fully open; a second ACV, an input of the second ACV being fluidically connected to the output of the first ACV, and an output of the second ACV being fluidically connected to a nozzle, the second ACV having positions ranging from fully closed to fully open; a proxy sensor configured to generate a proxy signal representing an indirect measure of a position of the first ACV; and a controller electrically connected to the first and second ACVs and the proxy sensor, the controller being configured to cause the second ACV to close based on the proxy signal and thereby stop flow of the liquid to the nozzle.

BACKGROUND

During fabrication, a semiconductor wafer is subjected to multipleprocesses in order to produce, eventually, multiple ICs from the wafer.Such multiple processes include deposition processes in whichcorresponding layers of material are deposited onto the surface of thewafer.

In a typical deposition process, a layer of photoresist material, suchas a tri-layer photoresist, is applied to the semiconductor substrate.Before such a deposition process, the surface of the wafer is subjectedto a substrate-preparation process in order to prepare the surface ofthe wafer to receive the photoresist. A substrate-preparation processtypically includes washing the surface of the wafer with a cleaningsolvent, then baking the wafer to promote dehydration, and thenspin-coating an adhesion promoter onto the wafer. Subsequently, thelayer of photoresist material is spin-coated onto the wafer. The layerof photoresist material is exposed to light (or other types of exposingradiation) in order to selectively change the solubility of the resistto a developer. After exposure, developer is applied to the layer ofnow-exposed photoresist material, e.g., by releasing the developer ontothe wafer as the wafer is spun (spin-releasing).

Each of the washing, the spin-coating of the adhesion promoter, thespin-coating of the photoresist material and the spin-releasing of thedeveloper includes dispensing a liquid. Typically, an automatic controlvalve (ACV) such as a pneumatically-actuated valve is used to start andstop the flow of the liquid material onto the surface of the wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1D are diagrams of a drippage prevention system, in accordancewith at least one embodiment of the present disclosure.

FIGS. 1E-1F are pressure-plots (plots of pressures) corresponding to thefirst pressure sensor and the second pressure sensor in FIGS. 1A-1D, inaccordance with at least one embodiment of the present disclosure.

FIG. 2A is a diagram of another drippage prevention system, inaccordance with at least one embodiment of the present disclosure.

FIG. 2B is a diagram of another drippage prevention system, inaccordance with at least one embodiment of the present disclosure.

FIG. 3 is a diagram of another drippage prevention system, in accordancewith at least one embodiment of the present disclosure.

FIG. 4 is a diagram of another drippage prevention system, in accordancewith at least one embodiment of the present disclosure.

FIG. 5A is a flowchart of a method for operating a drippage preventionsystem, in accordance with at least one embodiment of the presentdisclosure.

FIG. 5B is a more detailed view of a block in the flowchart of FIG. 5A,in accordance with at least one embodiment of the present disclosure.

FIG. 5C is a more detailed view of blocks in the flowchart of FIG. 5A,in accordance with at least one embodiment of the present disclosure.

FIG. 5D is a more detailed view of another block in the flowchart ofFIG. 5A, in accordance with at least one embodiment of the presentdisclosure.

FIG. 6 is a block diagram of a general purpose computing device forimplementing the controller, accordance with one or more embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, values, operations, materials,arrangements, or the like, are described below to simplify the presentdisclosure. These are, of course, merely examples and are not intendedto be limiting. Other components, values, operations, materials,arrangements, or the like, are contemplated. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

In the context of integrated circuit (IC) fabrication, a semiconductorwafer is subjected to multiple processes including deposition processes.For a typical deposition process, each of the washing, the spin-coatingof the adhesion promoter, the spin-coating of the photoresist materialand the spin-releasing of the developer includes dispensing a liquidfrom a nozzle using a corresponding main automatic control valve (ACV),typically a pneumatically controlled ACV. If the main ACV does not fullyclose, then the flow of liquid is not stopped, e.g., resulting indrippage, where drippage is understood to mean drops of the liquidcontinuing to reach the wafer. Drippage associated with one or more ofthe multiple processes (to which the semiconductor wafer is subjected)would reduce the quality of the ICs which ultimately result from havingperformed the multiple processes on the wafer. At least some embodimentsof the present disclosure prevent drippage by providing a liquiddispensing system including: a main ACV retrofitted with a proxy sensor;and a backup ACV fluidically connected between the main ACV and thenozzle. The proxy sensor generates a proxy signal representing anindirect measure of a position of the first ACV. A controller causes thebackup ACV to close based on the proxy signal.

FIGS. 1A-1D are diagrams of a drippage prevention system 100, inaccordance with at least one embodiment of the present disclosure.

System 100 includes: a source 102 of a fluid, e.g., a liquid(liquid-source 102), which is to be dispensed; a main automatic controlvalve (ACV) 104; a fluidic connection, e.g., a pipe 106, whichfluidically connects liquid-source 102 to main ACV 104; a backup ACV108; a fluidic connection, e.g., a pipe 110, which fluidically connectsmain ACV 104 to backup ACV 108; a nozzle 112 from which the fluid/liquidis dispensed; a fluidic connection, e.g., a pipe 113, which fluidicallyconnects backup ACV 108 to nozzle 112; and a wafer-spinning arrangement115.

Main ACV 104 is a pneumatically actuated ACV. Main ACV 104 includes: abody 124A; a bonnet 124B mechanically connected to body 124A; a cylinder124C mechanically connected to bonnet 124B; an axially-movable piston126A in cylinder 124C; a diaphragm 126B in body 124A; a stem 126Cmechanically connecting piston 126A to diaphragm 126B; a spring 126Darranged inside cylinder 124C and on a side of piston 126A opposite tostem 126C; and a weir 126E fixed in body 124A. A weir is a saddle or aseat against which a pinch-portion of diaphragm 126B can be brought intocontact. Cylinder 124C has two pneumatic ports: a first pneumatic port127A, which is located on the side of piston 126A opposite to the sideon which spring 126D is located; and a second pneumatic port 127B, whichis located on the same side of piston 126A as spring 126D.

Backup ACV 108 also is a pneumatically actuated ACV. Backup ACV 108includes: a body 128A; a bonnet 128B mechanically connected to body128A; a cylinder 128C mechanically connected to bonnet 128B; anaxially-movable piston 130A in cylinder 128C; a diaphragm 130B in body128A; a stem 130C mechanically connecting piston 130A to diaphragm 130B;a spring 130D arranged inside cylinder 128C and on the same side ofpiston 130A as stem 130C; and a weir 130E fixed in body 128A. Cylinder128C includes two pneumatic ports: a first pneumatic port 131A, which islocated on the side of piston 130A opposite to the side on which spring130D is located; and a second pneumatic port 131B, which is located onthe same side of piston 130A as spring 130D.

System 100 further includes: a first source 140 of air (air-source 140);a first current-to-pressure (I/P) converter 142; an optional firsttemperature sensor 144; a proxy sensor 145; an optional secondtemperature sensor 148; a second air-source 152; a second I/P converter154; and a controller 156. Proxy sensor 145 is a pressure sensingarrangement which includes a first pressure sensor 146 and a secondpressure sensor 150. In some embodiments, first air-source 140 andsecond air-source 152 are the same apparatus/device. In someembodiments, first I/P converter 142 and second I/P converter 154 arethe same apparatus/device.

First I/P converter 142 is fluidically connected to first air-source140. First temperature sensor 144 is fluidically connected to first I/Pconverter 142. First pressure sensor 146 of proxy sensor 145 isfluidically connected to first temperature sensor 144 and to firstpneumatic port 127A of cylinder 124C. In some embodiments, first I/Pconverter 142 includes an air-release valve (not shown) by whichair-pressure is controllably released from the overall/cumulativefluidic connection between first I/P converter 142 and first pneumaticport 127A of cylinder 124C. Second pressure sensor 150 of proxy sensor145 is fluidically connected to second temperature sensor 148 and tosecond pneumatic port 127B of cylinder 124C. Second I/P converter 154 isfluidically connected to second air-source 152 and to second pneumaticport 127B of cylinder 124C. Details regarding I/P converters andarrangements including the same, in general, are found in U.S. Pat. No.5,251,148, granted Oct. 5, 1993, and U.S. Pat. No. 5,558,115, grantedSep. 24, 1996, the entirety of each of which is hereby incorporated byreference.

Controller 156 is electrically connected to first I/P converter 142,first temperature sensor 144, first pressure sensor 146, secondtemperature sensor 148, second pressure sensor 150, and second I/Pconverter 154. Controller 156 receives: first and second pressuresignals from corresponding first pressure sensor 146 and second pressuresensor 150 of proxy sensor 145; and first and second temperature signalsfrom corresponding first temperature sensor 144 and second temperaturesensor 148. The first pressure signal from first pressure sensor 146represents pressure of air on the same side of piston 126A as firstpneumatic port 127A of cylinder 124C. The second pressure signal fromsecond pressure sensor 150 represents air pressure on the same side ofpiston 126A as second pneumatic port 127B of cylinder 124C. The firsttemperature signal from first temperature sensor 144 representstemperature of air on the same side of piston 126A as first pneumaticport 127A of cylinder 124C. The second temperature signal from secondtemperature sensor 148 represents temperature of air on the same side ofpiston 126A as second pneumatic port 127B of cylinder 124C.

Based on the process for which the liquid being sourced by liquid-source102 is being used, controller 156 generates a first control signal andprovides the first control signal to first I/P converter 142 in order toselectively open/close main ACV 104. Based on the first and secondpressure signals and the first and second temperature signals,controller 156 generates a second control signal and provides the secondcontrol signal to second I/P converter 154 in order to selectivelyopen/close backup ACV 108.

Diaphragm 126B (of body 124A of main ACV 104) is formed of a resilientmaterial. In a closed position corresponding to a non-actuated (ordefault) state of main ACV 104 (which is shown in FIG. 1A), stem 126Cforces a pinch-portion of diaphragm 126B into contact with weir 126E,thereby blocking the flow of liquid from pipe 106 to pipe 110. In anopen position corresponding to an actuated state of main ACV 104 (whichis shown in FIG. 1B), first I/P converter 142 (according to the firstcontrol signal from controller 156), provides air pressure to overcomethe bias force on piston 126A (applied by spring 126D) and thereby movepiston 126A away from weir 126E such that stem 126C pulls thepinch-portion of diaphragm 126B away from weir 126E, thereby unblockingthe flow of liquid from pipe 106 to pipe 110. Main ACV 104 has beenshown with weir configuration. In some embodiments, main ACV 104 has astraight-through configuration such there is no weir 126E.

Diaphragm 130B (of body 128A of backup ACV 108) is formed of a resilientmaterial. In an open position corresponding to a non-actuated state ofbackup ACV 108 (which is shown in FIG. 1A), spring 130D has forcedpiston 130A away from weir 130E such that stem 130C pulls thepinch-portion of diaphragm 130B away from weir 130E, thereby unblockingthe flow of liquid from pipe 110 to pipe 113. In a closed positioncorresponding to an actuated state of backup ACV 108 (which is shown inFIG. 1B), second I/P converter 154 (according to the second controlsignal from controller 156), provides air pressure to overcome the biasforce on piston 130A (applied by spring 130D) and thereby moves piston130A toward weir 130E such that stem 130C forces the pinch-portion ofdiaphragm 130B into contact with weir 130E, thereby blocking the flow ofliquid from pipe 110 to pipe 113. Backup ACV 108 has been shown withweir configuration. In some embodiments, backup ACV 108 has astraight-through configuration such there is no weir 130E.

Wafer-spinning arrangement 115 includes: a semiconductor wafer 116; arotatable table 118 on which wafer 116 is disposed; a motor 120; and ashaft 122 mechanically connecting rotatable table 118 to motor 120. Insome embodiments, relative to a fixed position of nozzle 112,wafer-spinning arrangement 115 is moveable/translatable in at least twodirections. In some embodiments, relative to a fixed position ofwafer-spinning arrangement 115, nozzle 112 is moveable/translatable inat least two directions. In some embodiments, each of wafer-spinningarrangement 115 and nozzle 112 is moveable/translatable in at least twodirections.

In FIG. 1A, controller 156 has controlled main ACV 104 to be in theclosed position corresponding to the non-actuated state of main ACV 104and has controlled backup ACV 108 to be in the open positioncorresponding to the non-actuated state of backup ACV 108. Because mainACV 104 is in the closed position, stem 126C forces the pinch-portion ofdiaphragm 126B into contact with weir 126E, thereby blocking the flow ofliquid from pipe 106 to pipe 110, hence no drops of liquid are shownbetween nozzle 112 and wafer 116.

In FIG. 1B, controller 156 has controlled main ACV 104 to be in the openposition corresponding to the actuated state of main ACV 104 and hascontrolled backup ACV 108 to be in the open position corresponding tothe non-actuated state of backup ACV 108. Because main ACV is in theopen position, stem 126C pulls the pinch-portion of diaphragm 126B awayfrom weir 126E, thereby unblocking the flow of liquid from pipe 106 topipe 110. Because backup ACV 108 is in the open position, stem 130Cpulls a pinch-portion of diaphragm 130B away from weir 130E, therebyunblocking the flow of liquid from pipe 110 to pipe 113. As such, liquidis dispensed from nozzle 112, hence drops 114 of liquid are shownbetween nozzle 112 and wafer 116.

In FIG. 1C, controller 156 has attempted to control main ACV 104 to bein the closed position corresponding to the non-actuated state of mainACV 104 and has controlled backup ACV 108 to be in the open positioncorresponding to the non-actuated state of backup ACV 108. For a varietyof reasons, main ACV 104 may not fully close, as is shown in FIG. 1C.Possible reasons include generation of an insufficient biasing force byspring 126D due to aging, increased friction between the circumferentialface of piston 126A and the walls of cylinder 124C of main ACV 104, orthe like. Because main ACV 104 is not fully closed, stem 126C does notforce the pinch-portion of diaphragm 126B into contact with weir 126E,thereby permitting a small flow of liquid to pass from pipe 106 to pipe110. The small flow of liquid is less than when the main ACV 104 is in afull open position and more than when the main ACV 104 is in a fullyclosed position. Because backup ACV 108 is in the open position, thesmall flow of liquid passes from pipe 110 to pipe 113, hence drops 114of liquid are shown between nozzle 112 and wafer 116. Because FIG. 1Cconcerns a smaller flow of liquid than FIG. 1B, fewer drops 114 areshown in FIG. 1C than are shown in FIG. 1B.

In FIG. 1D, controller 156 has attempted to control main ACV 104 to bein the closed position corresponding to the non-actuated state of mainACV 104 and has controlled backup ACV 108 to be in the closed positioncorresponding to the actuated state of backup ACV 108. Further, in FIG.1D, main ACV 104 has not fully closed. As noted, for a variety ofreasons, main ACV 104 may not full close, as is shown in FIG. 1D. Basedon the first and second pressure signals and the first and secondtemperature signals, controller 156 has recognized that main ACV 104 hasnot fully closed, and accordingly has controlled backup ACV 108 to be inthe closed position. Because backup ACV 108 is in the closed position,stem 130C forces the pinch-portion of diaphragm 130B into contact withweir 130E, thereby blocking the flow of liquid from pipe 110 to pipe113, hence no drops of liquid are shown between nozzle 112 and wafer116.

In contrast to another sensing arrangement which would directly measurea position of the pinch-portion of diaphragm 126B relative to weir 126E,proxy sensor 145, and more particularly each of first pressure sensor146 and second pressure sensor 150, measures a corresponding parameter(namely, pressure) which is indirectly reflective of the position of thepinch-portion of diaphragm 126B. As such, each of first and secondpressure signals from corresponding first pressure sensor 146 and secondpressure sensor 150 is described as a proxy (or substitute) for adirectly measured position of the pinch-portion of diaphragm 126B.Together, first pressure sensor 146 and second pressure sensor 150together comprise proxy sensor 145, where proxy sensor 145 is a retrofitsubstitute for a sensor which otherwise would directly measure theposition of the pinch-portion of diaphragm 126B relative to weir 126E.

FIGS. 1E-1F are pressure-plots (plots of pressures) 160 and 166corresponding to first pressure sensor 146 and second pressure sensor150, in accordance with at least one embodiment of the presentdisclosure.

For simplicity of illustration, pressure-plots 160 and 166 arehypothetical examples. In FIGS. 1E-1F, the X-axis represents incrementsof time and the Y-axis represents increments of pressure. Forsimplicity, FIGS. 1E-1F show a brief range of time, namely times t0-t6.In some embodiments, other ranges of time are contemplated. Also forsimplicity, FIGS. 1E-1F show a range of pressures, namely pressuress0-s7. In some embodiments, other ranges of pressure are contemplated.

Pressure plot 160 includes a line 162 and a line 164. Line 162 is apiecewise function which represents reference (or expected) values forthe first pressure signal generated by first pressure sensor 146. Line164 is a piecewise function which represents sampled (or actual ormeasured) values for the first pressure signal generated by firstpressure sensor 146. In some embodiments, line 162 is continuous. Insome embodiments, line 162 is a piecewise continuous function. In someembodiments, line 162 is based on empirical data. In some embodiments,line 162 is based on calculated/modeled data.

Pressure plot 166 includes a line 168 and a line 170. Line 168 is apiecewise function which represents reference (or expected) values forthe second pressure signal generated by second pressure sensor 150. Line170 is a piecewise function which represents sampled (or actual ormeasured) values for the second pressure signal generated by secondpressure sensor 150. In some embodiments, line 168 is continuous. Insome embodiments, line 168 is a piecewise continuous function. In someembodiments, line 168 is based on empirical data. In some embodiments,line 168 is based on calculated/modeled data.

To extend the hypothetical examples which pressure plots 160 and 166represent, at time t0, let main ACV 104 be in the closed positioncorresponding to the non-actuated state of main ACV 104. As such, attime t0, each of the reference value (on line 162) for the firstpressure signal (generated by first pressure sensor 146), the sampledvalue (on line 164) of the first pressure signal (generated by firstpressure sensor 146), the reference value (on line 168) for the secondpressure signal (generated by second pressure sensor 150), and thesampled value (on line 170) of the second pressure signal (generated bysecond pressure sensor 150) has a minimum value, s0. In someembodiments, s0 is zero pressure.

From time t0 to time t3, let controller 156 actuate main ACV 104 bycontrolling first I/P converter 142 to increase the air pressureprovided to first pneumatic port 127A of cylinder 124C. Accordingly, thereference value (on line 162) for the first pressure signal and thecorresponding sampled value (on line 164) of the first pressure signalprogressively increase over times t1, t2 and t3. As piston 126A is movedaway from first pneumatic port 127A toward second pneumatic port 127B,the air in the fluidic connection between second pneumatic port 127B andsecond pressure sensor 150 will become progressively more compressedsuch that air pressure will progressively increase. Accordingly, thereference value (on line 168) for the second pressure signal and thecorresponding sampled value (on line 170) of the second pressure signalprogressively increase at times t1, t2 and t3. At time t3, main ACV 104is expected to be in the open position corresponding to the actuatedstate of main ACV 104.

From time t3 to time t6, let controller 156 de-actuate main ACV 104 bycontrolling first I/P converter 142 to release the air pressure providedto first pneumatic port 127A of cylinder 124C. Accordingly, thereference value (on line 162) for the first pressure signal and thecorresponding sampled value (on line 164) of the first pressure signalprogressively decrease over times t4, t5 and t6. As piston 126A is movedtoward first pneumatic port 127A and away from second pneumatic port127B, the air in the fluidic connection between second pneumatic port127B and second pressure sensor 150 will become progressively lesscompressed such that air pressure will progressively decrease.Accordingly, the reference value (on line 168) for the second pressuresignal and the corresponding sampled value (on line 170) of the secondpressure signal progressively decrease at times t4, t5 and t6.

At time t6, main ACV 104 is expected (once again) to be in the closedposition corresponding to the non-actuated state of main ACV 104. Assuch, at time t6, each of the reference value (on line 162) for thefirst pressure signal (generated by first pressure sensor 146), thesampled value (on line 164) of the first pressure signal (generated byfirst pressure sensor 146), and the reference value (on line 168) forthe second pressure signal (generated by second pressure sensor 150)again has the minimum value, s0. For purposes of discussion, it isassumed that the sampled value (on line 170) of the second pressuresignal (generated by second pressure sensor 150) does not have theminimum value sO but instead has the value s2, where s0<s2. A possibleexplanation for the sampled value (on line 170) of the second pressuresignal (generated by second pressure sensor 150) having the value s2 attime t6 is that piston 126A has not been moved sufficiently close tofirst pneumatic port 127A of cylinder 124C. When piston 126A has notbeen moved sufficiently close to first pneumatic port 127A, stem 126Cwill not have forced the pinch-portion of diaphragm 126B into contactwith weir 126E (thereby permitting a small flow of liquid to pass frompipe 106 to pipe 110), which represents a failure state of main ACV 104.

In operation, controller 156: receives the first pressure signal fromfirst pressure sensor 146 and generates line 164; and receives thesecond pressure signal from second pressure sensor 150 and generatesline 170. Also, controller 156: receives the first temperature signalfrom first temperature sensor 144 and adjusts a first threshold valuebased on the first temperature signal; and receives the secondtemperature signal from second temperature sensor 148 and adjusts asecond threshold value based on the second temperature signal. Detailsregarding temperature-related adjustments, e.g., in the context ofcompressibility, are found in U.S. Pat. No. 5,251,148, incorporatedabove. In some embodiments, controller 156 does not adjust the first andsecond thresholds based on the corresponding first and secondtemperature signals. Accordingly, in some embodiments, system 100 doesnot include first temperature sensor 144 and second temperature sensor148.

Controller 156 compares measured values on line 164 againstcorresponding reference values on line 162, determines correspondingfirst differences Δ1(t), and compares the first differences Δ1(t)against the first threshold value. Also, controller 156 comparesmeasured values on line 170 against corresponding reference values online 168, determines corresponding second differences Δ2(t), andcompares the second differences Δ2(t) against the second thresholdvalue.

In some embodiments, if either an instance of the first difference Δ1(t)exceeds the first threshold value or an instance of the seconddifference Δ2(t) exceeds the second threshold value, then controller 156recognizes that main ACV 104 has not fully closed, and main ACV 104 isin a failure state. Returning to the hypothetical examples of pressureplots 160 and 166, it is assumed that the sampled value (on line 170) ofthe second pressure signal (generated by second pressure sensor 150) att6 is s2 (line_170(t6)=s2), and that the difference between the sampledvalue sampled value (line 170) and the reference value (on line 168) attime t6 (line_168(t6)=s0) exceeds the second threshold (thresh2), whereΔ2(t6)=line_170(t6)-1in_168(t6)=s2−s0 such that thresh2<Δ2(t6). Upondetermining that main ACV 104 is in a failure state, controller 156generates the second control signal, which causes the backup ACV 108 toclose. In some embodiments, controller 156 also triggers an alarm. Suchan alarm notifies a user that main ACV 104 is in the failure state andis in need of repair and/or adjustment.

FIG. 2A is a diagram of a drippage prevention system 200A, in accordancewith at least one embodiment of the present disclosure.

In FIG. 2A, system 200A is similar to system 100 where similar albeitdifferent components in system 200A have been assigned a referencenumber that is increased by 100 relative to corresponding components insystem 100. For brevity of description, the discussion will focus ondifferences in system 200A with respect to system 100.

System 200A differs from system 100 in that system 200A does not includefirst temperature sensor 144 and first pressure sensor 146. Accordingly,system 200A includes: a proxy sensor 245A instead of proxy sensor 145,where proxy sensor 245A includes second pressure sensor 150; and acontroller 256A instead of controller 156. Among other things,controller 256A receives the second temperature signal from secondtemperature sensor 148 and adjusts the second threshold value based onthe second temperature signal. In some embodiments, controller 256A doesnot adjust the second threshold based on the second temperature signal.Accordingly, in some embodiments, system 200A does not include secondtemperature sensor 148.

FIG. 2B is a diagram of a drippage prevention system 200B, in accordancewith at least one embodiment of the present disclosure.

In FIG. 2A, system 200B is similar to system 100 where similar albeitdifferent components in system 200B have been assigned a referencenumber that is increased by 100 relative to corresponding components insystem 100. For brevity of description, the discussion will focus ondifferences in system 200B with respect to system 100.

System 200B differs from system 100 in that system 200A does not includesecond temperature sensor 148 and second pressure sensor 150.Accordingly, system 200B includes: a proxy sensor 245B instead of proxysensor 145, where proxy sensor 245B includes first pressure sensor 146;and a controller 256B instead of controller 156. Among other things,controller 256B receives the first second temperature signal from firsttemperature sensor 144 and adjusts the first threshold value based onthe first temperature signal. In some embodiments, controller 256B doesnot adjust the first threshold based on the first temperature signal.Accordingly, in some embodiments, system 200B does not include firsttemperature sensor 144.

FIG. 3 is a diagram of a drippage prevention system 300, in accordancewith at least one embodiment of the present disclosure.

In FIG. 3, system 300 is similar to system 100 where similar albeitdifferent components in system 300 have been assigned a reference numberthat is increased by 200 relative to corresponding components in system100. For brevity of description, the discussion will focus ondifferences in system 300 with respect to system 100.

System 300 differs from system 100 in that system 300 does not include:first temperature sensor 144; first pressure sensor 146; secondtemperature sensor 148; and second pressure sensor 150. Accordingly,system 300 includes: a proxy sensor 345 instead of proxy sensor 145; anda controller 356 instead of controller 156. Proxy sensor 345 includes atleast one inductive sensor. In FIG. 3, proxy sensor 345 is shown asincluding a first inductive sensor 347A, a second inductive sensor 347B,a third inductive sensor 347C and a fourth inductive sensor 347D. Eachof inductive sensors 347A-347D generates a piston-position signal whichvaries depending on the position of piston 126A in cylinder 124C. Insome embodiments, the signals of inductive sensors 347A-347D exhibitsimilar variation. For example, when a midline of piston 126A isopposite inductive sensor 347A, the piston-position signal output byinductive sensor peaks. Details regarding inductively sensing position,in general, are found in U.S. Pat. No. 4,719,362, granted Jan. 12, 1988,and U.S. Pat. No. 5,264,733, granted Nov. 23, 1993, the entirety of eachof which is hereby incorporated by reference. Among other things,controller 356 receives and compares the piston-position signals ofinductive sensors 347A-347D and thereby determines a position of piston126A relative to inductive sensors 347A-347D.

If controller 356 determines that piston 126A is not in an appropriateposition when main ACV 104 is supposed to be in the closed position,then controller 356 determines main ACV 104 to be in a failure state.Upon determining that main ACV 104 is in a failure state, controller 356generates the second control signal, which causes the backup ACV 108 toclose. In some embodiments, controller 356 also triggers the alarm.

FIG. 4 is a diagram of a drippage prevention system 400, in accordancewith at least one embodiment of the present disclosure.

In FIG. 4, system 400 is similar to system 100 where similar albeitdifferent components in system 400 have been assigned a reference numberthat is increased by 300 relative to corresponding components in system100. For brevity of description, the discussion will focus ondifferences in system 400 with respect to system 100.

System 400 differs from system 100 in that system 400 does not include:first temperature sensor 144; first pressure sensor 146; secondtemperature sensor 148; and second pressure sensor 150. Accordingly,system 300 includes: a proxy sensor 445 instead of proxy sensor 145; anda controller 456 instead of controller 156. Proxy sensor 445 includes anoptical sensing arrangement 449. Optical sensing arrangement 449includes an optical emitter 451 and an optical receiver 453. Opticalsensing arrangement 449 generates a drippage signal which variesaccording to whether drops 114 (FIG. 1C) are present or not in the spacebetween optical emitter 451 and optical receiver 453. Details regardingan optical drop-sensing arrangement are found in U.S. Pre-GrantPublication No. 20150004720, published Jan. 1, 2015, the entirety ofwhich is hereby incorporated by reference. Among other things,controller 456 receives the signal from proxy sensor 445 (in particular,optical sensing arrangement 449) and thereby determines if drops 114(FIG. 1C) are present or not.

If controller 456 determines that drops 114 are present at a time whenmain ACV 104 is supposed to be in the closed position, then controller456 deems main ACV 104 to be in a failure state. Upon determining thatmain ACV 104 is in a failure state, controller 456 generates the secondcontrol signal, which causes the backup ACV 108 to close. In someembodiments, controller 456 also triggers the alarm.

FIG. 5A is a flowchart 502 of a method of operating a drippageprevention system, and thus is a method of preventing drippage in afluid dispensing system, in accordance with at least one embodiment ofthe present disclosure.

In FIG. 5A, flowchart 502 includes a block 504. At block 504, at least afirst proxy signal (e.g., the first pressure signal from proxy sensor146, the second pressure signal from second pressure sensor 150, thesignal from proxy sensor 345, the signal from proxy sensor 445, or thelike) is generated. The at least first proxy signal represents anindirect measure of the position of a first ACV (e.g., main ACV 104, orthe like), the first ACV having a position ranging from a fully closedposition to a fully open position. From block 504, flow proceeds to ablock 506.

At block 506, based on at least the first proxy signal, it is recognized(e.g., by controller 156, 356, 456 or the like) that the first ACV hasfailed to close, and thus a failure state exists. From block 506, flowproceeds to a block 508.

At block 508, a second ACV (e.g., backup ACV 108, or the like) is causedto close (e.g., under the control of controller 156, 356, 456 or thelike). Like the first ACV, the second ACV has a position ranging from afully closed position to a fully open position.

FIG. 5B is a more detailed view of block 504 of FIG. 5A, in accordancewith at least one embodiment of the present disclosure.

In FIG. 5B, block 504 includes blocks 510-512. At block 510, at least afirst pressure signal is generated representing air pressure at a firstport (e.g., second port 127B of main ACV 104, or the like) of the firstACV. From block 510, flow proceeds to block 512. At block 512, the firstproxy signal is set equal to the first pressure signal.

FIG. 5C is a more detailed view of blocks 504 and 506 of FIG. 5A, inaccordance with at least one embodiment of the present disclosure.

In FIG. 5B, block 504 includes blocks 510-516. Blocks 510-512 are thesame as in FIG. 5B. From bock 512, flow proceeds to a block 514. Atblock 514, at least a second pressure signal is generated representingair pressure at a second port (e.g., first port 127A of main ACV 104, orthe like) of the first ACV. From block 514, flow proceeds to block 516.At block 516, the second proxy signal is set equal to the secondpressure signal.

As noted, flow proceeds from block 504 to block 506. In FIG. 5B, block506 includes a block 518. At block 518, based on at least the secondproxy signal as well as the first proxy signal, it is recognized (e.g.,by controller 156, 356, 456 or the like) that the first ACV has failedto close, and thus a failure state exists.

FIG. 5D is a more detailed view of block 506 of FIG. 5A, in accordancewith at least one embodiment of the present disclosure.

In FIG. 5D, block 506 includes blocks 520-524. Blocks 520-524 areexecuted, e.g., by controller 156, 356, 456 or the like. At block 520, adifference between the proxy signal and a corresponding reference valueis determined. From block 520, flow proceeds to block 522. At block 522,the difference is compared against a deviation threshold. From block522, flow proceeds to block 524. At block 524, when the differenceexceeds the deviation threshold, it is determined that the failure stateexists.

One of ordinary skill in the art would recognize that operations areable to be removed or that additional operations are able to be added toat least one of the above-noted methods without departing from the scopeof this description. One of ordinary skill in the art would alsorecognize that an order of operations in at least one of the above-notedmethods is able to be adjusted without departing from the scope of thisdescription.

FIG. 6 is a block diagram of a controller 656, in accordance with someembodiments. Controllers 156, 256A, 256B, 356, 456 or the like areimplemented, for example, using controller 656.

In some embodiments, controller 656 is a general purpose computingdevice including a hardware processor 602 and a non-transitory,computer-readable storage medium 604. Storage medium 604, amongst otherthings, is encoded with, i.e., stores, computer program code 606, i.e.,a set of executable instructions. Execution of instructions 606 byhardware processor 602 represents (at least in part) a controller whichimplements a portion or all of, e.g., the method of preventing drippagein a fluid dispensing system, the methods of FIGS. 5A-6D, in accordancewith one or more embodiments (hereinafter, the methods).

Processor 602 is electrically coupled to computer-readable storagemedium 604 via a bus 608. Processor 602 is also electrically coupled toan I/O interface 610 by bus 608. A network interface 612 is alsoelectrically connected to processor 602 via bus 608. Network interface612 is connected to a network 614, so that processor 602 andcomputer-readable storage medium 604 are capable of connecting toexternal elements via network 614. Processor 602 is configured toexecute computer program code 606 encoded in computer-readable storagemedium 604 in order to cause system 600 to be usable for performing aportion or all of the noted methods. In one or more embodiments,processor 602 is a central processing unit (CPU), a multi-processor, adistributed processing system, an application specific integratedcircuit (ASIC), and/or a suitable processing unit.

In one or more embodiments, computer-readable storage medium 604 is anelectronic, magnetic, optical, electromagnetic, infrared, and/or asemiconductor system (or apparatus or device). For example,computer-readable storage medium 604 includes a semiconductor orsolid-state memory, a magnetic tape, a removable computer diskette, arandom access memory (RAM), a read-only memory (ROM), a rigid magneticdisk, and/or an optical disk. In one or more embodiments using opticaldisks, computer-readable storage medium 604 includes a compact disk-readonly memory (CD-ROM), a compact disk-read/write (CD-R/W), and/or adigital video disc (DVD).

In one or more embodiments, storage medium 604 stores computer programcode 606 configured to cause controller 656 (where such executionrepresents (at least in part) the controller) to be usable forperforming a portion or all of the methods. In one or more embodiments,storage medium 604 also stores information which facilitates performinga portion or all of the methods.

Controller 656 includes I/O interface 610. I/O interface 610 is coupledto external circuitry. In one or more embodiments, I/O interface 620includes a keyboard, keypad, mouse, trackball, trackpad, touchscreen,and/or cursor direction keys for communicating information and commandsto processor 602.

Controller 656 also includes network interface 612 coupled to processor602. Network interface 612 allows system 600 to communicate with network614, to which one or more other computer systems are connected. Networkinterface 612 includes wireless network interfaces such as BLUETOOTH,WIFI, WIMAX, GPRS, or WCDMA; or wired network interfaces such asETHERNET, USB, or IEEE-1364. In one or more embodiments, a portion orall of methods is/are implemented in two or more systems 600.

System 600 is configured to receive information through I/O interface610. The information received through I/O interface 610 includes one ormore of instructions, data, design rules, libraries of standard cells,and/or other parameters for processing by processor 602. The informationis transferred to processor 602 via bus 608. Controller 656 isconfigured to receive information related to a UI through I/O interface610. The information is stored in computer-readable medium 604 as userinterface (UI) 642.

In some embodiments, a portion or all of the noted methods isimplemented as a standalone software application for execution by aprocessor. In some embodiments, a portion or all of the noted methods isimplemented as a software application that is a part of an additionalsoftware application. In some embodiments, a portion or all of themethods is implemented as a plug-in to a software application. In someembodiments, at least one of the methods is implemented as a softwareapplication that is a portion of an EDA tool. In some embodiments, aportion or all of the methods is implemented as a software applicationthat is used by controller 656.

In some embodiments, the processes are realized as functions of aprogram stored in a non-transitory computer readable recording medium.Examples of a non-transitory computer readable recording medium include,but are not limited to, external/removable and/or internal/built-instorage or memory unit, e.g., one or more of an optical disk, such as aDVD, a magnetic disk, such as a hard disk, a semiconductor memory, suchas a ROM, a RAM, a memory card, and the like.

An aspect of the present disclosure is directed to a drippage preventionsystem including: a first automatic control valve (ACV), an input of thefirst ACV fluidically connected to a fluid-source of fluid to bedispensed, the first ACV having positions ranging from fully closed tofully open; a second ACV, an input of the second ACV being fluidicallyconnected to the output of the first ACV, and an output of the secondACV being fluidically connected to a nozzle, the second ACV havingpositions ranging from fully closed to fully open; a proxy sensorconfigured to generate a proxy signal representing an indirect measureof a position of the first ACV; and a controller electrically connectedto the first and second ACVs and the proxy sensor, the controller beingconfigured to cause the second ACV to close based on the proxy signaland thereby stop flow of the liquid to the nozzle.

Another aspect of the present disclosure is directed to a drippageprevention system including: a first pneumatically-controlled automaticcontrol valve (ACV), an input of the first ACV being fluidicallyconnected to a fluid-source of fluid to be dispensed, the first ACVbeing configured to be biased by a first spring to a fully closedposition in a non-actuated state, the first ACV having a first port on aside opposite the first spring; a second pneumatically-controlled ACV,an input of the second ACV being fluidically connected to the output ofthe first ACV, and an output of the second ACV being fluidicallyconnected to a nozzle, the second ACV being configured to be biased by asecond spring to a fully open position in a non-actuated state, thesecond ACV having a first port on a side opposite the second spring; acurrent (I) to pressure (P) converter (I/P converter), the I/P converterbeing fluidically connected to the first port of the first ACV, the I/Pconverter being configured to provide air pressure to dispose the firstACV into the fully open position in an actuated state; a pressuresensing arrangement including at least one of: a first pressure sensorconfigured to generate a first pressure signal representing air pressureat the first port of the first ACV; or a second pressure sensorconfigured to generate a second pressure signal representing airpressure at a second port of the first ACV; and a controller configuredto cause the second ACV to close based on at least one of the first orsecond pressure signals.

Another aspect of the present disclosure is directed to a method ofpreventing drippage in a fluid dispensing system which has a firstautomatic control valve (ACV), an input of the first ACV fluidicallyconnected to fluid-source of fluid to be dispensed, the first ACV havinga position ranging from fully closed to fully open, and a second ACV, aninput of the second ACV being fluidically connected to the output of thefirst ACV, and an output of the second ACV being fluidically connectedto a nozzle. Such a method includes: generating at least a first proxysignal representing at least a first indirect measure of a position ofthe first ACV, and recognizing, based on at least the first proxysignal, that a failure state exists in which the first ACV has failed toclose; and causing the second ACV to close when the failure stateexists.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A drippage prevention system comprising: a firstautomatic control valve (ACV), an input of the first ACV fluidicallyconnected to a fluid-source of fluid to be dispensed, the first ACVhaving positions ranging from fully closed to fully open; a second ACV,an input of the second ACV being fluidically connected to an output ofthe first ACV, and an output of the second ACV being fluidicallyconnected to a nozzle, the second ACV having positions ranging fromfully closed to fully open; a proxy sensor configured to generate aproxy signal representing an indirect measure of a position of the firstACV; and a controller electrically connected to the first and secondACVs and electrically connected to the proxy sensor, the controllerbeing configured to cause the second ACV to close based on the proxysignal and thereby stop flow of liquid to the nozzle.
 2. The system ofclaim 1, wherein: the first ACV is a pneumatically-controlled valveconfigured to be biased by a spring to a fully closed position in anon-actuated state; the first ACV has a first port on a side oppositethe spring; the system further comprises: a current (I) to pressure (P)converter (I/P converter) electrically connected to the controller, theI/P converter having a first port fluidically connected to an air-sourceof pressurized air and a second port fluidically connected to the firstport of the first ACV, the I/P converter being configured to provide airpressure to dispose the first ACV into a fully open position in anactuated state; the proxy sensor includes: a first pressure sensorconfigured to generate a first pressure signal representing air pressureat the first port of the first ACV; and the proxy signal is the firstpressure signal.
 3. The system of claim 2, further comprising: atemperature sensor configured to generate a temperature signalrepresenting air temperature at the first port of the first ACV; andwherein the controller is further configured to cause the second ACV toclose based also on the temperature signal.
 4. The system of claim 2,wherein: the first ACV has a second port on a same side as the spring;the proxy sensor further includes: a second pressure sensor configuredto generate a second pressure signal representing air pressure at thesecond port of the first ACV; and the controller is further configuredto cause the second ACV to close based also on the second pressuresignal.
 5. The system of claim 4, further comprising: a temperaturesensor configured to generate a temperature signal representing airtemperature at the second port of the first ACV; and wherein thecontroller is further configured to cause the second ACV to close basedalso on the temperature signal.
 6. The system of claim 1, wherein: thefirst ACV is a pneumatically-controlled valve configured to be biased bya spring to a fully closed position in a non-actuated state; the firstACV has a first port on a side opposite the spring and a second port ona same side as the spring; the system further comprises: a current (I)to pressure (P) converter (I/P converter) having a first portfluidically connected to an air-source of pressurized air and a secondport fluidically connected to the first port of the first ACV, the I/Pconverter being configured to provide air pressure to dispose the firstACV into a fully open position in an actuated state; the proxy sensorincludes: a pressure sensor configured to generate a pressure signalrepresenting air pressure at the second port of the first ACV; and theproxy signal is the pressure signal.
 7. The system of claim 6, furthercomprising: a temperature sensor configured to generate a temperaturesignal representing air temperature at the second port of the first ACV;and wherein the controller is further configured to cause the second ACVto close based also on the temperature signal.
 8. The system of claim 1,wherein: the first ACV is a pneumatically-controlled valve including apiston, a spring, a diaphragm and a stem which mechanically connects thepiston to the diaphragm, the first ACV being biased by the spring to afully closed position in a non-actuated state; the first ACV has a firstport on a side opposite the spring and a second port on a same side asthe spring; the system further comprises: a current (I) to pressure (P)converter (I/P converter) electrically connected to the controller, theI/P converter having a first port fluidically connected to an air-sourceof pressurized air and a second port fluidically connected to the firstport of the first ACV, the I/P converter being configured to provide airpressure to dispose the first ACV into a fully open position in anactuated state; the proxy sensor includes: a first inductive sensorconfigured to generate a first piston-position signal representing acorresponding first position of the piston; and the proxy signal is thefirst piston-position signal.
 9. The system of claim 8, wherein: theproxy signal is a first proxy signal; the proxy sensor is furtherconfigured to generate at least a second proxy signal; the controller isfurther configured to cause the second ACV to close based also on thefirst and second proxy signals; the system further comprises: at least asecond inductive sensor configured to generate at least a secondpiston-position signal representing at least a corresponding secondposition of the piston; and the second proxy signal is the secondpiston-position signal.
 10. The system of claim 1, wherein: the firstACV is a pneumatically-controlled valve configured to be biased by aspring to a fully closed position in a non-actuated state; the first ACVhas a first port on a side opposite the spring; the system furthercomprises: a current (I) to pressure (P) converter (I/P converter)electrically connected to the controller, the I/P converter having afirst port fluidically connected to an air-source of pressurized air anda second port fluidically connected to the first port of the first ACV,the I/P converter being configured to provide air pressure to disposethe first ACV into a fully open position in an actuated state; the proxysensor includes: an optical sensing arrangement configured opticallysense drippage at the nozzle and accordingly generate a drippage signal;and the proxy signal is the drippage signal.
 11. The system of claim 10,wherein: the optical sensing arrangement includes: an optical emitterconfigured to emit an optical signal; and an optical receiver configuredto receive the optical signal from the optical emitter; and wherein whenliquid is dispensed from the nozzle, then reception of the opticalsignal by the optical receiver is interrupted; wherein the drippagesignal is indicative of whether the reception of the optical signal isinterrupted; and the controller is further configured to cause thesecond ACV to close based on when the drippage signal indicates that thereception of the optical signal is interrupted.
 12. The system of claim1, wherein: the second ACV is a pneumatically-controlled valveconfigured to be biased by a spring to a fully open position in anon-actuated state; the second ACV has a first port on a side oppositethe spring; and the system further comprises: a current (I) to pressure(P) converter (I/P converter) electrically connected to the controller,the I/P converter having a first port fluidically connected to anair-source of pressurized air and a second port fluidically connected tothe first port of the second ACV, the I/P converter being configured toprovide air pressure to dispose the second ACV into a fully closedposition in an actuated state.
 13. The system of claim 1, wherein thecontroller is further configured to: recognize, based on the proxysignal, that a failure state exists in which the first ACV has failed toclose; and cause the second ACV to close when the failure state exists.14. The system of claim 13, wherein the controller is configured torecognize that a failure state exists by being further configured to:determine a difference between the proxy signal and a correspondingreference value; compare the difference against a deviation threshold;and determine the failure state to exist when the difference exceeds thedeviation threshold.
 15. A drippage prevention system comprising: afirst pneumatically-operated automatic control valve (ACV), an input ofthe first ACV being fluidic ally connected to a fluid-source of fluid tobe dispensed, the first ACV being configured to be biased by a firstspring to a fully closed position in a non-actuated state, the first ACVhaving a first port on a side opposite the first spring; a secondpneumatically-operated ACV, an input of the second ACV being fluidicallyconnected to an output of the first ACV, and an output of the second ACVbeing fluidically connected to a nozzle, the second ACV being configuredto be biased by a second spring to a fully open position in anon-actuated state, the second ACV having a first port on a sideopposite the second spring; a current (I) to pressure (P) converter (I/Pconverter) the I/P converter being fluidically connected to the firstport of the first ACV, the I/P converter being configured to provide airpressure to dispose the first ACV into the fully open position in anactuated state; a pressure sensing arrangement including at least oneof: a first pressure sensor configured to generate a first pressuresignal representing air pressure at the first port of the first ACV; ora second pressure sensor configured to generate a second pressure signalrepresenting air pressure at a second port of the first ACV; and acontroller configured to cause the second ACV to close based on at leastone of the first or second pressure signals.
 16. The system of claim 15,wherein the controller is further configured to cause the second ACV toclose which includes being further configured to: determine at least onedifference between the at least one of the first or second pressuresignals and a corresponding at least one reference value; compare the atleast one difference against a deviation threshold; and determine afailure state to exist when one or more of the at least one differenceexceeds the deviation threshold.
 17. A method of preventing drippage ina fluid dispensing system which has a first automatic control valve(ACV), an input of the first ACV fluidically connected to fluid-sourceof fluid to be dispensed, the first ACV having positions ranging fromfully closed to fully open, and a second ACV, an input of the second ACVbeing fluidically connected to an output of the first ACV, and an outputof the second ACV being fluidically connected to a nozzle, the secondACV having positions ranging from fully closed to fully open, the methodcomprising: generating at least a first proxy signal representing atleast a first indirect measure of a position of the first ACV,recognizing, based on at least the first proxy signal, that a failurestate exists in which the first ACV has failed to close; and causing thesecond ACV to close when the failure state exists.
 18. The method ofclaim 17, wherein: the generating at least a first proxy signalincludes: generating a first pressure signal representing air pressureat a first port of the first ACV; and the first proxy signal is thefirst pressure signal.
 19. The method of claim 18, wherein: thegenerating at least a first proxy signal further generates at least asecond proxy signal representing at least a second indirect measure ofthe position of the first ACV, and the generating at least a first proxysignal further includes: generating a second pressure signalrepresenting air pressure at a second port of the first ACV; the secondproxy signal is the second pressure signal; and the recognizing that afailure state exists is also based on the second pressure signal. 20.The method of claim 18, wherein the recognizing that a failure stateexists includes: determining at least a first difference between the atleast first proxy signal and a corresponding at least first referencevalue; comparing the at least first difference against a deviationthreshold; and determining the failure state to exist when the at leastfirst difference exceeds the deviation threshold.